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KEY MESSAGES

- Severe thunderstorm risk across south central SD this afternoon and evening with large hail and damaging winds as the primary threats, though a tornado can't be ruled out.

- Chance of severe weather with all hazards possible Thursday.

- Warming temperatures expected into the weekend.

DISCUSSION

(This Evening Through Wednesday) Issued at 1250 PM MDT Wed Jun 3 2026

Visible satellite shows cloud cover over much of western SD with ongoing storms over north central SD. Skies have cleared out over Wyoming and the Black Hills with water vapor imagery showing narrow plume of mid level moisture streaming into south central SD. Sfc cold front makes its way across the eastern tier of the CWA through this afternoon and evening. Plume of 50-60F dewpoints and moderate instability of 2000-3000 J/kg SB CAPE will support thunderstorm development along the front. Mid-level flow will strengthen as the shortwave approaches with deep layer shear increasing to 30-40 kts which will support organized convection and rotating updrafts. CAMs are once again struggling with timing and storm mode with the HRRR continuing to push back development over south central SD until later this evening (after 6 to 7 pm) while the NAM and RRFS both show storms developing somewhat earlier (around the 4 to 5 pm MDT timeframe). Storms may start off as discrete cells, capable of large hail, damaging winds, and a low tornado risk. Storms will quickly coalesce into a line as the front pushes through with the primary threat transitioning to damaging wind gusts.

Attention turns to tomorrow where severe thunderstorms are once again possible across much of the forecast area. Another shortwave moving along nearly zonal flow will eject over the Northern Plains by the afternoon hours. Strengthening mid level flow will support deep layer shear values of 30 to 40 kts with SBCAPE values climbing to 2000-3000+ J/kg with the highest values across southwestern SD. This looks to be a typical northern Black Hills supercell environment, capable of very large hail (2+"), though a tornado or two can't be entirely ruled out. As storms push eastward over the plains through the evening hours, they may transition into an MCS with associated severe wind threat.

Things settle down for most of the CWA Friday as shortwave ridging builds to our west. Storms are still possible over south- central SD as the sfc front and shortwave exit the region. In addition, diurnally driven showers can't be ruled out over the Black Hills in the afternoon. Shortwave ridge will move over the region by Saturday and bring hot and dry conditions to the CWA. Storm chances return Sunday as upper level trof deepens over the western US and places our CWA under unsettled southwest flow.

AVIATION

(For the 18Z TAFS Through 18Z Thursday) Issued At 1127 AM MDT Wed Jun 3 2026

Low ceilings will continue to burn off in northeast WY and east of the Black Hills over the next hour or so. After which, VFR conditions are expected at both TAF sites until early Thursday morning (~12Z). Low clouds will redevelop across the area, bringing back MVFR/IFR conditions.

UNR WATCHES/WARNINGS/ADVISORIES

SD...None. WY...None.